/*

   * linux/fs/jbd2/recovery.c

   *
   * Written by Stephen C. Tweedie <sct@redhat.com>, 1999
   *
   * Copyright 1999-2000 Red Hat Software --- All Rights Reserved
   *
   * This file is part of the Linux kernel and is made available under
   * the terms of the GNU General Public License, version 2, or at your
   * option, any later version, incorporated herein by reference.
   *
   * Journal recovery routines for the generic filesystem journaling code;
   * part of the ext2fs journaling system.
   */
  
  #ifndef __KERNEL__
  #include "jfs_user.h"
  #else
  #include <linux/time.h>
  #include <linux/fs.h>

  #include <linux/jbd2.h>

  #include <linux/errno.h>

  #include <linux/crc32.h>

  #endif
  
  /*
   * Maintain information about the progress of the recovery job, so that
   * the different passes can carry information between them.
   */
  struct recovery_info
  {
  	tid_t		start_transaction;
  	tid_t		end_transaction;
  
  	int		nr_replays;
  	int		nr_revokes;
  	int		nr_revoke_hits;
  };
  
  enum passtype {PASS_SCAN, PASS_REVOKE, PASS_REPLAY};
  static int do_one_pass(journal_t *journal,
  				struct recovery_info *info, enum passtype pass);
  static int scan_revoke_records(journal_t *, struct buffer_head *,
  				tid_t, struct recovery_info *);
  
  #ifdef __KERNEL__
  
  /* Release readahead buffers after use */
  static void journal_brelse_array(struct buffer_head *b[], int n)
  {
  	while (--n >= 0)
  		brelse (b[n]);
  }
  
  
  /*
   * When reading from the journal, we are going through the block device
   * layer directly and so there is no readahead being done for us.  We
   * need to implement any readahead ourselves if we want it to happen at
   * all.  Recovery is basically one long sequential read, so make sure we
   * do the IO in reasonably large chunks.
   *
   * This is not so critical that we need to be enormously clever about
   * the readahead size, though.  128K is a purely arbitrary, good-enough
   * fixed value.
   */
  
  #define MAXBUF 8
  static int do_readahead(journal_t *journal, unsigned int start)
  {
  	int err;
  	unsigned int max, nbufs, next;

  	unsigned long long blocknr;

  	struct buffer_head *bh;
  
  	struct buffer_head * bufs[MAXBUF];
  
  	/* Do up to 128K of readahead */
  	max = start + (128 * 1024 / journal->j_blocksize);
  	if (max > journal->j_maxlen)
  		max = journal->j_maxlen;
  
  	/* Do the readahead itself.  We'll submit MAXBUF buffer_heads at
  	 * a time to the block device IO layer. */
  
  	nbufs = 0;
  
  	for (next = start; next < max; next++) {

  		err = jbd2_journal_bmap(journal, next, &blocknr);

  
  		if (err) {

  			printk(KERN_ERR "JBD2: bad block at offset %u
  ",

  				next);
  			goto failed;
  		}
  
  		bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
  		if (!bh) {
  			err = -ENOMEM;
  			goto failed;
  		}
  
  		if (!buffer_uptodate(bh) && !buffer_locked(bh)) {
  			bufs[nbufs++] = bh;
  			if (nbufs == MAXBUF) {
  				ll_rw_block(READ, nbufs, bufs);
  				journal_brelse_array(bufs, nbufs);
  				nbufs = 0;
  			}
  		} else
  			brelse(bh);
  	}
  
  	if (nbufs)
  		ll_rw_block(READ, nbufs, bufs);
  	err = 0;
  
  failed:
  	if (nbufs)
  		journal_brelse_array(bufs, nbufs);
  	return err;
  }
  
  #endif /* __KERNEL__ */
  
  
  /*
   * Read a block from the journal
   */
  
  static int jread(struct buffer_head **bhp, journal_t *journal,
  		 unsigned int offset)
  {
  	int err;

  	unsigned long long blocknr;

  	struct buffer_head *bh;
  
  	*bhp = NULL;
  
  	if (offset >= journal->j_maxlen) {

  		printk(KERN_ERR "JBD2: corrupted journal superblock
  ");

  		return -EIO;
  	}

  	err = jbd2_journal_bmap(journal, offset, &blocknr);

  
  	if (err) {

  		printk(KERN_ERR "JBD2: bad block at offset %u
  ",

  			offset);
  		return err;
  	}
  
  	bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
  	if (!bh)
  		return -ENOMEM;
  
  	if (!buffer_uptodate(bh)) {
  		/* If this is a brand new buffer, start readahead.
                     Otherwise, we assume we are already reading it.  */
  		if (!buffer_req(bh))
  			do_readahead(journal, offset);
  		wait_on_buffer(bh);
  	}
  
  	if (!buffer_uptodate(bh)) {

  		printk(KERN_ERR "JBD2: Failed to read block at offset %u
  ",

  			offset);
  		brelse(bh);
  		return -EIO;
  	}
  
  	*bhp = bh;
  	return 0;
  }
  
  
  /*
   * Count the number of in-use tags in a journal descriptor block.
   */

  static int count_tags(journal_t *journal, struct buffer_head *bh)

  {
  	char *			tagp;
  	journal_block_tag_t *	tag;

  	int			nr = 0, size = journal->j_blocksize;
  	int			tag_bytes = journal_tag_bytes(journal);

  
  	tagp = &bh->b_data[sizeof(journal_header_t)];

  	while ((tagp - bh->b_data + tag_bytes) <= size) {

  		tag = (journal_block_tag_t *) tagp;
  
  		nr++;

  		tagp += tag_bytes;

  		if (!(tag->t_flags & cpu_to_be32(JBD2_FLAG_SAME_UUID)))

  			tagp += 16;

  		if (tag->t_flags & cpu_to_be32(JBD2_FLAG_LAST_TAG))

  			break;
  	}
  
  	return nr;
  }
  
  
  /* Make sure we wrap around the log correctly! */
  #define wrap(journal, var)						\
  do {									\
  	if (var >= (journal)->j_last)					\
  		var -= ((journal)->j_last - (journal)->j_first);	\
  } while (0)
  
  /**

   * jbd2_journal_recover - recovers a on-disk journal

   * @journal: the journal to recover
   *
   * The primary function for recovering the log contents when mounting a
   * journaled device.
   *
   * Recovery is done in three passes.  In the first pass, we look for the
   * end of the log.  In the second, we assemble the list of revoke
   * blocks.  In the third and final pass, we replay any un-revoked blocks
   * in the log.
   */

  int jbd2_journal_recover(journal_t *journal)

  {

  	int			err, err2;

  	journal_superblock_t *	sb;
  
  	struct recovery_info	info;
  
  	memset(&info, 0, sizeof(info));
  	sb = journal->j_superblock;
  
  	/*
  	 * The journal superblock's s_start field (the current log head)
  	 * is always zero if, and only if, the journal was cleanly
  	 * unmounted.
  	 */
  
  	if (!sb->s_start) {
  		jbd_debug(1, "No recovery required, last transaction %d
  ",
  			  be32_to_cpu(sb->s_sequence));
  		journal->j_transaction_sequence = be32_to_cpu(sb->s_sequence) + 1;
  		return 0;
  	}
  
  	err = do_one_pass(journal, &info, PASS_SCAN);
  	if (!err)
  		err = do_one_pass(journal, &info, PASS_REVOKE);
  	if (!err)
  		err = do_one_pass(journal, &info, PASS_REPLAY);

  	jbd_debug(1, "JBD2: recovery, exit status %d, "

  		  "recovered transactions %u to %u
  ",
  		  err, info.start_transaction, info.end_transaction);

  	jbd_debug(1, "JBD2: Replayed %d and revoked %d/%d blocks
  ",

  		  info.nr_replays, info.nr_revoke_hits, info.nr_revokes);
  
  	/* Restart the log at the next transaction ID, thus invalidating
  	 * any existing commit records in the log. */
  	journal->j_transaction_sequence = ++info.end_transaction;

  	jbd2_journal_clear_revoke(journal);

  	err2 = sync_blockdev(journal->j_fs_dev);
  	if (!err)
  		err = err2;

  	return err;
  }
  
  /**

   * jbd2_journal_skip_recovery - Start journal and wipe exiting records

   * @journal: journal to startup
   *
   * Locate any valid recovery information from the journal and set up the
   * journal structures in memory to ignore it (presumably because the
   * caller has evidence that it is out of date).
   * This function does'nt appear to be exorted..
   *
   * We perform one pass over the journal to allow us to tell the user how
   * much recovery information is being erased, and to let us initialise
   * the journal transaction sequence numbers to the next unused ID.
   */

  int jbd2_journal_skip_recovery(journal_t *journal)

  {
  	int			err;

  
  	struct recovery_info	info;
  
  	memset (&info, 0, sizeof(info));

  
  	err = do_one_pass(journal, &info, PASS_SCAN);
  
  	if (err) {

  		printk(KERN_ERR "JBD2: error %d scanning journal
  ", err);

  		++journal->j_transaction_sequence;
  	} else {

  #ifdef CONFIG_JBD2_DEBUG

  		int dropped = info.end_transaction - 
  			be32_to_cpu(journal->j_superblock->s_sequence);

  		jbd_debug(1,

  			  "JBD2: ignoring %d transaction%s from the journal.
  ",

  			  dropped, (dropped == 1) ? "" : "s");

  #endif

  		journal->j_transaction_sequence = ++info.end_transaction;
  	}
  
  	journal->j_tail = 0;
  	return err;
  }

  static inline unsigned long long read_tag_block(int tag_bytes, journal_block_tag_t *tag)

  {

  	unsigned long long block = be32_to_cpu(tag->t_blocknr);

  	if (tag_bytes > JBD2_TAG_SIZE32)

  		block |= (u64)be32_to_cpu(tag->t_blocknr_high) << 32;
  	return block;
  }

  /*
   * calc_chksums calculates the checksums for the blocks described in the
   * descriptor block.
   */
  static int calc_chksums(journal_t *journal, struct buffer_head *bh,
  			unsigned long *next_log_block, __u32 *crc32_sum)
  {
  	int i, num_blks, err;
  	unsigned long io_block;
  	struct buffer_head *obh;
  
  	num_blks = count_tags(journal, bh);
  	/* Calculate checksum of the descriptor block. */
  	*crc32_sum = crc32_be(*crc32_sum, (void *)bh->b_data, bh->b_size);
  
  	for (i = 0; i < num_blks; i++) {
  		io_block = (*next_log_block)++;
  		wrap(journal, *next_log_block);
  		err = jread(&obh, journal, io_block);
  		if (err) {

  			printk(KERN_ERR "JBD2: IO error %d recovering block "

  				"%lu in log
  ", err, io_block);
  			return 1;
  		} else {
  			*crc32_sum = crc32_be(*crc32_sum, (void *)obh->b_data,
  				     obh->b_size);
  		}

  		put_bh(obh);

  	}
  	return 0;
  }

  static int do_one_pass(journal_t *journal,
  			struct recovery_info *info, enum passtype pass)
  {
  	unsigned int		first_commit_ID, next_commit_ID;
  	unsigned long		next_log_block;
  	int			err, success = 0;
  	journal_superblock_t *	sb;
  	journal_header_t *	tmp;
  	struct buffer_head *	bh;
  	unsigned int		sequence;
  	int			blocktype;

  	int			tag_bytes = journal_tag_bytes(journal);

  	__u32			crc32_sum = ~0; /* Transactional Checksums */

  	/*
  	 * First thing is to establish what we expect to find in the log
  	 * (in terms of transaction IDs), and where (in terms of log
  	 * block offsets): query the superblock.
  	 */
  
  	sb = journal->j_superblock;
  	next_commit_ID = be32_to_cpu(sb->s_sequence);
  	next_log_block = be32_to_cpu(sb->s_start);
  
  	first_commit_ID = next_commit_ID;
  	if (pass == PASS_SCAN)
  		info->start_transaction = first_commit_ID;
  
  	jbd_debug(1, "Starting recovery pass %d
  ", pass);
  
  	/*
  	 * Now we walk through the log, transaction by transaction,
  	 * making sure that each transaction has a commit block in the
  	 * expected place.  Each complete transaction gets replayed back
  	 * into the main filesystem.
  	 */
  
  	while (1) {
  		int			flags;
  		char *			tagp;
  		journal_block_tag_t *	tag;
  		struct buffer_head *	obh;
  		struct buffer_head *	nbh;

  		cond_resched();

  
  		/* If we already know where to stop the log traversal,
  		 * check right now that we haven't gone past the end of
  		 * the log. */
  
  		if (pass != PASS_SCAN)
  			if (tid_geq(next_commit_ID, info->end_transaction))
  				break;
  
  		jbd_debug(2, "Scanning for sequence ID %u at %lu/%lu
  ",
  			  next_commit_ID, next_log_block, journal->j_last);
  
  		/* Skip over each chunk of the transaction looking
  		 * either the next descriptor block or the final commit
  		 * record. */

  		jbd_debug(3, "JBD2: checking block %ld
  ", next_log_block);

  		err = jread(&bh, journal, next_log_block);
  		if (err)
  			goto failed;
  
  		next_log_block++;
  		wrap(journal, next_log_block);
  
  		/* What kind of buffer is it?
  		 *
  		 * If it is a descriptor block, check that it has the
  		 * expected sequence number.  Otherwise, we're all done
  		 * here. */
  
  		tmp = (journal_header_t *)bh->b_data;

  		if (tmp->h_magic != cpu_to_be32(JBD2_MAGIC_NUMBER)) {

  			brelse(bh);
  			break;
  		}
  
  		blocktype = be32_to_cpu(tmp->h_blocktype);
  		sequence = be32_to_cpu(tmp->h_sequence);
  		jbd_debug(3, "Found magic %d, sequence %d
  ",
  			  blocktype, sequence);
  
  		if (sequence != next_commit_ID) {
  			brelse(bh);
  			break;
  		}
  
  		/* OK, we have a valid descriptor block which matches
  		 * all of the sequence number checks.  What are we going
  		 * to do with it?  That depends on the pass... */
  
  		switch(blocktype) {

  		case JBD2_DESCRIPTOR_BLOCK:

  			/* If it is a valid descriptor block, replay it

  			 * in pass REPLAY; if journal_checksums enabled, then
  			 * calculate checksums in PASS_SCAN, otherwise,
  			 * just skip over the blocks it describes. */

  			if (pass != PASS_REPLAY) {

  				if (pass == PASS_SCAN &&
  				    JBD2_HAS_COMPAT_FEATURE(journal,
  					    JBD2_FEATURE_COMPAT_CHECKSUM) &&
  				    !info->end_transaction) {
  					if (calc_chksums(journal, bh,
  							&next_log_block,
  							&crc32_sum)) {
  						put_bh(bh);
  						break;
  					}
  					put_bh(bh);
  					continue;
  				}

  				next_log_block += count_tags(journal, bh);

  				wrap(journal, next_log_block);

  				put_bh(bh);

  				continue;
  			}
  
  			/* A descriptor block: we can now write all of
  			 * the data blocks.  Yay, useful work is finally
  			 * getting done here! */
  
  			tagp = &bh->b_data[sizeof(journal_header_t)];

  			while ((tagp - bh->b_data + tag_bytes)

  			       <= journal->j_blocksize) {
  				unsigned long io_block;
  
  				tag = (journal_block_tag_t *) tagp;
  				flags = be32_to_cpu(tag->t_flags);
  
  				io_block = next_log_block++;
  				wrap(journal, next_log_block);
  				err = jread(&obh, journal, io_block);
  				if (err) {
  					/* Recover what we can, but
  					 * report failure at the end. */
  					success = err;

  					printk(KERN_ERR
  						"JBD2: IO error %d recovering "

  						"block %ld in log
  ",
  						err, io_block);
  				} else {

  					unsigned long long blocknr;

  
  					J_ASSERT(obh != NULL);

  					blocknr = read_tag_block(tag_bytes,
  								 tag);

  
  					/* If the block has been
  					 * revoked, then we're all done
  					 * here. */

  					if (jbd2_journal_test_revoke

  					    (journal, blocknr,
  					     next_commit_ID)) {
  						brelse(obh);
  						++info->nr_revoke_hits;
  						goto skip_write;
  					}
  
  					/* Find a buffer for the new
  					 * data being restored */
  					nbh = __getblk(journal->j_fs_dev,
  							blocknr,
  							journal->j_blocksize);
  					if (nbh == NULL) {
  						printk(KERN_ERR

  						       "JBD2: Out of memory "

  						       "during recovery.
  ");
  						err = -ENOMEM;
  						brelse(bh);
  						brelse(obh);
  						goto failed;
  					}
  
  					lock_buffer(nbh);
  					memcpy(nbh->b_data, obh->b_data,
  							journal->j_blocksize);

  					if (flags & JBD2_FLAG_ESCAPE) {

  						*((__be32 *)nbh->b_data) =

  						cpu_to_be32(JBD2_MAGIC_NUMBER);

  					}
  
  					BUFFER_TRACE(nbh, "marking dirty");
  					set_buffer_uptodate(nbh);
  					mark_buffer_dirty(nbh);
  					BUFFER_TRACE(nbh, "marking uptodate");
  					++info->nr_replays;
  					/* ll_rw_block(WRITE, 1, &nbh); */
  					unlock_buffer(nbh);
  					brelse(obh);
  					brelse(nbh);
  				}
  
  			skip_write:

  				tagp += tag_bytes;

  				if (!(flags & JBD2_FLAG_SAME_UUID))

  					tagp += 16;

  				if (flags & JBD2_FLAG_LAST_TAG)

  					break;
  			}
  
  			brelse(bh);
  			continue;

  		case JBD2_COMMIT_BLOCK:

  			/*     How to differentiate between interrupted commit
  			 *               and journal corruption ?
  			 *
  			 * {nth transaction}
  			 *        Checksum Verification Failed
  			 *			 |
  			 *		 ____________________
  			 *		|		     |
  			 * 	async_commit             sync_commit
  			 *     		|                    |
  			 *		| GO TO NEXT    "Journal Corruption"
  			 *		| TRANSACTION
  			 *		|
  			 * {(n+1)th transanction}
  			 *		|
  			 * 	 _______|______________
  			 * 	|	 	      |
  			 * Commit block found	Commit block not found
  			 *      |		      |
  			 * "Journal Corruption"       |
  			 *		 _____________|_________
  			 *     		|	           	|
  			 *	nth trans corrupt	OR   nth trans
  			 *	and (n+1)th interrupted     interrupted
  			 *	before commit block
  			 *      could reach the disk.
  			 *	(Cannot find the difference in above
  			 *	 mentioned conditions. Hence assume
  			 *	 "Interrupted Commit".)
  			 */
  
  			/* Found an expected commit block: if checksums
  			 * are present verify them in PASS_SCAN; else not
  			 * much to do other than move on to the next sequence

  			 * number. */

  			if (pass == PASS_SCAN &&
  			    JBD2_HAS_COMPAT_FEATURE(journal,
  				    JBD2_FEATURE_COMPAT_CHECKSUM)) {
  				int chksum_err, chksum_seen;
  				struct commit_header *cbh =
  					(struct commit_header *)bh->b_data;
  				unsigned found_chksum =
  					be32_to_cpu(cbh->h_chksum[0]);
  
  				chksum_err = chksum_seen = 0;
  
  				if (info->end_transaction) {

  					journal->j_failed_commit =
  						info->end_transaction;

  					brelse(bh);
  					break;
  				}
  
  				if (crc32_sum == found_chksum &&
  				    cbh->h_chksum_type == JBD2_CRC32_CHKSUM &&
  				    cbh->h_chksum_size ==
  						JBD2_CRC32_CHKSUM_SIZE)
  				       chksum_seen = 1;
  				else if (!(cbh->h_chksum_type == 0 &&
  					     cbh->h_chksum_size == 0 &&
  					     found_chksum == 0 &&
  					     !chksum_seen))
  				/*
  				 * If fs is mounted using an old kernel and then
  				 * kernel with journal_chksum is used then we
  				 * get a situation where the journal flag has
  				 * checksum flag set but checksums are not
  				 * present i.e chksum = 0, in the individual
  				 * commit blocks.
  				 * Hence to avoid checksum failures, in this
  				 * situation, this extra check is added.
  				 */
  						chksum_err = 1;
  
  				if (chksum_err) {
  					info->end_transaction = next_commit_ID;

  					if (!JBD2_HAS_INCOMPAT_FEATURE(journal,

  					   JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)){

  						journal->j_failed_commit =
  							next_commit_ID;

  						brelse(bh);
  						break;
  					}
  				}
  				crc32_sum = ~0;
  			}

  			brelse(bh);
  			next_commit_ID++;
  			continue;

  		case JBD2_REVOKE_BLOCK:

  			/* If we aren't in the REVOKE pass, then we can
  			 * just skip over this block. */
  			if (pass != PASS_REVOKE) {
  				brelse(bh);
  				continue;
  			}
  
  			err = scan_revoke_records(journal, bh,
  						  next_commit_ID, info);
  			brelse(bh);
  			if (err)
  				goto failed;
  			continue;
  
  		default:
  			jbd_debug(3, "Unrecognised magic %d, end of scan.
  ",
  				  blocktype);
  			brelse(bh);
  			goto done;
  		}
  	}
  
   done:
  	/*
  	 * We broke out of the log scan loop: either we came to the
  	 * known end of the log or we found an unexpected block in the
  	 * log.  If the latter happened, then we know that the "current"
  	 * transaction marks the end of the valid log.
  	 */

  	if (pass == PASS_SCAN) {
  		if (!info->end_transaction)
  			info->end_transaction = next_commit_ID;
  	} else {

  		/* It's really bad news if different passes end up at
  		 * different places (but possible due to IO errors). */
  		if (info->end_transaction != next_commit_ID) {

  			printk(KERN_ERR "JBD2: recovery pass %d ended at "

  				"transaction %u, expected %u
  ",
  				pass, next_commit_ID, info->end_transaction);
  			if (!success)
  				success = -EIO;
  		}
  	}
  
  	return success;
  
   failed:
  	return err;
  }
  
  
  /* Scan a revoke record, marking all blocks mentioned as revoked. */
  
  static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
  			       tid_t sequence, struct recovery_info *info)
  {

  	jbd2_journal_revoke_header_t *header;

  	int offset, max;

  	int record_len = 4;

  	header = (jbd2_journal_revoke_header_t *) bh->b_data;
  	offset = sizeof(jbd2_journal_revoke_header_t);

  	max = be32_to_cpu(header->r_count);

  	if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_64BIT))
  		record_len = 8;
  
  	while (offset + record_len <= max) {

  		unsigned long long blocknr;

  		int err;

  		if (record_len == 4)
  			blocknr = be32_to_cpu(* ((__be32 *) (bh->b_data+offset)));
  		else
  			blocknr = be64_to_cpu(* ((__be64 *) (bh->b_data+offset)));
  		offset += record_len;

  		err = jbd2_journal_set_revoke(journal, blocknr, sequence);

  		if (err)
  			return err;
  		++info->nr_revokes;
  	}
  	return 0;
  }